If you no longer marvel at the Internet's power to connect and transform the world, you need to hear the story of a woman known to many around the globe as, loosely translated, Dog Poop Girl.

Recently, the woman was on the subway in her native South Korea when her dog decided that this was a good place to do its business.

The woman made no move to clean up the mess, and several fellow travelers got agitated. The woman allegedly grew belligerent in response.

What happened next was a remarkable show of Internet force, and a peek into an unsettling corner of the future.

One of the train riders took pictures of the incident with a camera phone and posted them on a popular Web site. Net dwellers soon began to call her by the unflattering nickname, and issued a call to arms for more information about her.

According to one blog that has covered the story, "within days, her identity and her past were revealed. Requests for information about her parents and relatives started popping up and people started to recognize her by the dog and the bag she was carrying," because her face was partially obscured by her hair.

Online discussion groups crackled with chatter about every shred of the woman's life that could be found, and with debate over whether the Internet mob had gone too far. The incident became national news in South Korea and even was discussed in Sunday sermons in Korean churches in the Washington area.

Humiliated in public and indelibly marked, the woman reportedly quit her university.

Using the Internet as a tool to settle scores is hardly new. Search for any major retailer and you'll probably also find some kind of www.that-store-stinks.com Web site, with complaints about products or service.

Increasingly, the Internet also is a venue of so-called citizen journalism, in which swarms of surfers mobilize to gather information on what the traditional media isn't covering, or is covering in a way that dissatisfies some people.

But what happens when the two converge, and the Internet populace is stirred to action against individuals?

The Dog Poop Girl case "involves a norm that most people would seemingly agree to -- clean up after your dog," wrote Daniel J. Solove, a George Washington University law professor who specializes in privacy issues, on one blog. "But having a permanent record of one's norm violations is upping the sanction to a whole new level . . . allowing bloggers to act as a cyber-posse, tracking down norm violators and branding them with digital scarlet letters."

Howard Rheingold, who studies and writes about the impact of technology on the behavior of groups, said the debate should begin with an understanding that the rules of privacy have changed.

"The shadow side of the empowerment that comes with a billion and a half people being online is the surveillance aspect," he said. "We used to worry about big brother -- the state -- but now of course it's our neighbors, or people on the subway."

With society awash in personal data that is bought and sold daily, those who would use it as a weapon have few barriers.

When hackers get mad at each other they sometimes strike back by making public online the personal information of their adversary, a practice known as "dropping docs."

At the same time, it is easy to imagine the benefits of coordinated Internet posses to help track down those wanted for crimes, or to help solve mysteries.

It was the clarion call of one well-known blogger, for example, that led to answers about the dubious press credentials of Jeff Gannon, who attended White House news conferences and asked questions that favored President Bush and attacked Democrats.

But the mob went further, reporting and speculating on aspects of Gannon's private life.

"Where the line is between doing what the media or the legal system won't do is a pretty interesting question, and I don't have the answer," said Dan Gillmor, a former newspaper columnist who now is organizing citizen-journalism projects. "People have to think about consequences."

In discussions with dozens of people about this story, and in reading comments on blogs, I found an intriguing common thread. The instinct of most was to accept using the Internet as a new social-enforcement tool, but to search for that point on the continuum where enough was too much.

Putting Dog Poop Girl's picture on the Web was OK, some said, but not the clamoring for more information that followed. Others said the woman's face and other identifying features should have been obscured more. Still others said she was entitled to no privacy at all.

But there was also this, on the blog of Don Park:

"What would I have done if I was at the scene? I would have just cleaned up the mess without saying anything. . . . [The] mess is cleaned up and the girl, embarrassed at the right level."